However, Southgate confirmed the Football Association’s medical staff had checked with United and both were deemed as being not fit to report for England duty ahead of the World Cup qualifier with Scotland.

That goes against Mourinho’s accusation and Southgate insisted that neither player is “flaky”.

However, he claimed that some players have avoided pulling on the England shirt in the past.

England interim boss Southgate said: “I don’t know Chris well. But that wouldn’t be my impression (that he is flaky), having worked with him. I know Luke well and he’s had a really tough injury.

“There have been players that haven’t played as much when I was playing, maybe playing for England was a bit too much for them."

Smalling has not appeared for United since their defeat at Chelsea last month when it is believed he had two pain killing injections in a foot injury, while Shaw has struggled to recover from a horrific leg break last season.

They are both arguably first choice defenders for England when fully fit and Southgate admitted that Shaw was still struggling “with something” in his leg when he reported up in September.

Luke Shaw was also criticised by his manager (Image: Action Images via Reuters)

Southgate added: “After an injury as severe as that, we’ve got to handle that with care as well. With any injury, any recovery, there’s physical and psychological aspects to that, whether that’s an injury of a week or months.

“That is definitely part of the process of getting a player back into playing. Maybe that at times is to be aggressive and maybe that at times is to be supportive.

“There can be different approaches towards that because sometimes you might need a nudge to say, ‘Come on, you can.’

"But I can’t comment on the two guys because I don’t know the real specifics of exactly where they’re at.”

Southgate revealed that he has insisted some players report up this time despite them having fitness doubts. They are hopeful that Tottenham right back Kyle Walker will overcome an ankle problem but the FA are determined to take a tough stand.